fix(esp-sync): sync non-donation subscription data even if no completed orders

[dkoo]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Currently, for purposes of ESP contact syncing, a reader's "current product" can only be an active subscription or an inactive subscription with at least one completed order. This latter criteria is so that readers with donations that only have failed payments can't be considered "Ex-Donors", as they've never completed a donation. However, for non-donation subscriptions, we simply sync the subscription status, so it's more beneficial to sync data about these subscriptions whether or not they had any completed orders. This is especially important for sites with migrated subscriptions, most of which won't have any completed orders.

How to test the changes in this Pull Request:

1. Register a new reader account, then log into My Account and go to /my-account/add-payment-method to add a new payment method.
2. Add the "Decline after attaching" test card number: 4000000000000341 and save. This can be saved as a payment method without being declined up-front, but will be declined when attempting to use it to complete a transaction.
3. While still logged in as this reader, purchase a donation subscription (it will fail at the payment step—this is okay, the subscription will still be created in on-hold status, which is what we want).
4. In the connected ESP, inspect the synced contact data and confirm that no product data was synced (Product Name, Membership Status, Subscription Start/End/Last Payment/Next Payment Date fields).
5. While still logged in as this reader, purchase a NON-donation subscription.
6. In the connected ESP, inspect the synced contact data and confirm that the non-donation subscription product data was synced.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[matticbot]

🎉 This PR is included in version 5.11.3 🎉

The release is available on GitHub release

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